This invention relates to laundry machines, and more particularly, to automatic clothes washers that have a water temperature control, and to a method of controlling the water temperature.
Controlling the mixing of hot and cold water introduced into an automatic washing machine has been known for many years. By controlling the hot and cold water valves of the machine, the temperature of the mixed water may be regulated. Typically a temperature responsive switch, such as a thermostat, is located downstream of the water valves to sense the temperature of the mixed water and through approximate control and circuit means the opening and closing of the hot and cold water valves is controlled responsive to some predetermined temperature setting of the thermostat. One such typical arrangement is shown and described in U.S. Pat. No. 2,844,320 wherein the water valves are controlled by a thermostat located along a mutual output water line to the washing machine tub. Such an arrangement, however, has been found to detrimentally affect both the thermostat and the water valves due to their excessive cycling on and off because of the rapid changes in the water temperature in the output water line.
Another arrangement that has been utilized is shown and described in U.S. Pat. No. 2,533,624 wherein the thermostat is located in a temperature sensing relationship with the washing machine tub which contains the mixed water. U.S. Pat. No. 2,619,284 also shows a thermostat located on the tub. Such an arrangement, however, results in some basic difficulties. In most automatic washing machines there is an adjustment for the clothes load and therefore the level of water introduced into the tub for a given washing operation. The thermostat cannot have a fixed ideal location on the tub as the level of the mixed water varies. Another problem is that the long time delay in the thermostat sensing the change in temperature of the relatively large volume of water in the tub does not allow for accurately controlling the water valves to regulate the mixed water temperature.
Controlling mixing of hot and cold water can be mechanically controlled by having the hot water temperature control mixing of the hot and cold and the mixed temperature controlling the cold water flow as is shown and described in U.S. Pat. No. 3,007,644. This mechanical control valve has particular application for use in a hot water line as from a boiler so that the temperature of the water to a sink, wash tub, or appliance is maintained below a predetermined single elevated temperature. There are also mixing valves such as the mixing valve disclosed in U.S Pat. No. 2,747,801 wherein a thermostatic rod having a single maximum elevated temperature limit may be used to mechanically adjust the hot and cold mixing. Such a mixing valve, however, can be bypassed for very hot water if the user of the domestic appliance so desires.
Therefore, in the prior art water temperature control arrangements for clothes washers, sometimes the control is so sensitive to changes in temperature of the mixed water leaving the water valve that the thermostat and valve excessively cycle on and off, thus detrimentally affecting the life of those components. In some cases the sensing of the water in the tub is not accurate and maintaining the proper temperature control of the mixed water is not achieved. In some other cases a single maximum elevated temperature limit is preset into a mechanical device which device in most cases is quite complicated in design and operation and may be capable of being bypassed above the maximum elevated temperature.
By my invention, I have provided an automatic clothes washer with an improved water temperature control and method which can control either of two different selectable temperature levels such that the water filling the washer will always be maintained below either of the predetermined and preselected temperature levels. Moreover, this invention is an electromechanical system which is easy to implement, is quite low in cost and is effective to produce the desired results.